A disastrous end to 2017 means 2018 could be even worse

It is easy to overlook, amid our volatile politics, that the nation has not seen anything like this before.

Such is the scale of the 45th Parliament's unravelling that reporters have struggled to keep up and the Prime Minister has been unable to maintain a consistent line, much less project authority.

Failing governments, like fish, usually begin stinking from the head down. But Malcolm Turnbull faces no challenger. Instead, his parliamentary majority is drifting away for reasons that have nothing to do with policy nor internal dissatisfaction with his management.

It's a constitutional crisis removed from the leadership, and in many voters' estimation, detached from common sense. But that does not make it less real.

Reporters at Turnbull's inaugural press conference in Da Nang for Friday's APEC summit, simply dispensed with the usual politeness of first inquiring about the international agenda.

Should John Alexander and others stand down and refer themselves to the High Court?

Turnbull's response stacked up fine against any measure except perhaps his own. "Look, the fundamental point is that if you are satisfied that you are not constitutionally eligible to sit in the Parliament, then you shouldn't be sitting there - that's the fundamental principle," he began.

Voters will note that this is the same PM who defiantly kept Barnaby Joyce and Fiona Nash in cabinet. And they'll remember that immediately after the High Court chucked them out, Joyce admitted he had never believed he was constitutionally qualified. The deputy PM no less.

Senate president Stephen Parry's spectacular post-case resignation and a conga-line of dual allegiance cases unearthed since, have only deepened the crisis.

Now there is internecine warfare over Nash's casual vacancy with the Nationals hoping the Liberals' Hollie Hughes will be ruled ineligible, allowing Nash to re-enter the game.

But the Liberals' Jim Molan believes he would be the rightful beneficiary.

Meanwhile more MPs are under question, a reshuffle looms, the opposition and government continue to point score, and parliamentary sittings could be delayed, imperilling commitments such as marriage equality.